A MOSSBAUER-EFFECT STUDY ON THE ACICULAR COBALT FERRITE PARTICLES

The causes of the coercivity enhancement and the coercivity instabilit y of acicular cobalt ferrite particles containing 0-9.2 wt% Fe2+ ions under the influence of magnetic field and temperature were investigate d by means of transverse magnetic field annealing, torque, and Mossbau er experiments. The coercivity enhancement and the instability of Co m odified iron oxide particles are closely related to the uniaxial magne tic anisotropy. A Fe2+-CO2+ pair model was proposed to explain the uni axial magnetic anisotropy of Co modified iron particles. To verify the nature of the Fe2+-Co2+ pair, the probability of one or more Co ions appearing in the neighborhood of a B site Fe2+ ion was calculated usin g the chemical composition, the Mossbauer parameters, Pi(Fe2+) and Pi( Fe+3) and discussed conditions for forming the pair between the neares t-neighbor Co2+ and Fe2+ ion.